This study is designed to further investigations of adaptive changes in skeletal and osseous tissue associated with alterations in muscle length. Alterations in muscle length occur normally during growth but may also be induced in the craniofacial regions by modifications of the intermaxillary space and by orthognathic surgical procedures. Our primary objective is to broaden our understanding of the structure and function of the muscles of the craniofacial regions and to determine the adaptations that occur in the craniofacial musculature and the associated hard tissue resulting from alterations in muscle length. The emphasis in this proposed continuation period is in skeletal and muscular alterations following decreases in muscle length. Several experimental models will be used including partial and complete removal of the dentition. Adaptations will be studied by cephalometric, electromyographic, histochemical, biochemical and physiological techniques that we have used previously in studies of craniofacial adaptations. Data and interpretations gained from this study will be combined with data gained from our previous experimental investigations, leading to a better understanding of adaptations in the complex musculature of the craniofacial region.